Hijack the web to promote the deflationary spiral

A Diamond Club mega-value reader calls my attention to some of the amazing things being done with the Greasemonkey extension to the Firefox browser, which allows annotation to websites. The guys over at Overstimulate are doing some interesting things to deliver open source comparison shopping in the online book and travel industries, and I wonder what guerilla marketing opportunities we may see develop around this. (Someone else has been working on an extension for browser based BitTorrent, but the trail seems to have gone cold.)